Ion implantation systems are used to impart impurities, known as dopant elements, into semiconductor substrates or wafers, commonly referred to as workpieces. In such systems, an ion source ionizes a desired dopant element, and the ionized impurity is extracted from the ion source as a beam of ions. The ion beam is directed (e.g., swept) across respective workpieces to implant ionized dopants within the workpieces. The dopant ions alter the composition of the workpieces causing them to possess desired electrical characteristics, such as may be useful for fashioning particular semiconductor devices, for example, transistors upon the substrates.
The continuing trend toward smaller electronic devices has presented an incentive to “pack” a greater number of smaller, more powerful and more energy efficient semiconductor devices onto individual wafers. This necessitates careful control over semiconductor fabrication processes, including ion implantation and more particularly to the avoidance of particle contamination during ion implantation of the wafers. The so-called particle contamination means particles (tiny piece of materials either from the beamline elements or from the wafer handling elements, in the range of sub-micrometers to micrometers) are implanted onto, or otherwise move onto the wafer surface and stay on the surface. Moreover, semiconductor devices are being fabricated upon larger workpieces to increase product yield. For example, wafers having a diameter of 300 mm or more are being utilized so that more devices can be produced on a single wafer. Such wafers are expensive and, thus, make it very desirable to mitigate waste, such as having to scrap an entire larger wafer due to the affects of particle contamination during ion implantation or blocking the wafer areas under the particles from being processed or implanted.
One of the key contributors of particles is beam strikes, for example, on the extraction electrodes, on the beam line wall, on the apertures along the beam line, and on the faraday cups. These particles are then carried along with the ion beam and reach the target parts or wafers as contaminates which may affect the quality, dose level uniformity, yield and reliability of the implanted parts.
Accordingly, there is a need for mitigating the effects of particle contamination due to beam strikes within an ion implanter to provide minimal particle contamination with uniform implantation over the whole wafer or work piece.